feat(tui): replace /clear double-press gate with a proper confirm overlay

The time-window gate felt wrong — users would hit /clear, read the
prompt, retype, and consistently blow past the window. Swapping to a
real yes/no overlay that blocks input like the existing Approval and
Clarify prompts.

- add ConfirmReq type + OverlayState.confirm + $isBlocked coverage
- ConfirmPrompt component (prompts.tsx): cancel row on top as the
  default, danger-coloured confirm row on the bottom, Y/N hotkeys,
  Enter on default = cancel, Esc/Ctrl+C cancel
- wire into PromptZone (appOverlays.tsx)
- /clear + /new now push onto the overlay instead of arming a timer
- HERMES_TUI_NO_CONFIRM=1 still skips the prompt for scripting
- drop the destructiveGate + createSlashHandler reset wiring
  (destructive.ts and its tests removed)

Refs #4069.

ui-tui/src/components/appOverlays.tsx

@@ -9,7 +9,7 @@ import { $uiState } from '../app/uiStore.js'
 import { FloatBox } from './appChrome.js'
 import { MaskedPrompt } from './maskedPrompt.js'
 import { ModelPicker } from './modelPicker.js'
-import { ApprovalPrompt, ClarifyPrompt } from './prompts.js'
+import { ApprovalPrompt, ClarifyPrompt, ConfirmPrompt } from './prompts.js'
 import { SessionPicker } from './sessionPicker.js'
 import { SkillsHub } from './skillsHub.js'
 
@@ -31,6 +31,23 @@ export function PromptZone({
     )
   }
 
+  if (overlay.confirm) {
+    const req = overlay.confirm
+
+    const onConfirm = () => {
+      patchOverlayState({ confirm: null })
+      req.onConfirm()
+    }
+
+    const onCancel = () => patchOverlayState({ confirm: null })
+
+    return (
+      <Box flexDirection="column" flexShrink={0} paddingX={1} paddingY={1}>
+        <ConfirmPrompt onCancel={onCancel} onConfirm={onConfirm} req={req} t={ui.theme} />
+      </Box>
+    )
+  }
+
   if (overlay.clarify) {
     return (
       <Box flexDirection="column" flexShrink={0} paddingX={1} paddingY={1}>

ui-tui/src/components/prompts.tsx

@@ -2,7 +2,7 @@ import { Box, Text, useInput } from '@hermes/ink'
 import { useState } from 'react'
 
 import type { Theme } from '../theme.js'
-import type { ApprovalReq, ClarifyReq } from '../types.js'
+import type { ApprovalReq, ClarifyReq, ConfirmReq } from '../types.js'
 
 import { TextInput } from './textInput.js'
 
@@ -151,6 +151,80 @@ export function ClarifyPrompt({ cols = 80, onAnswer, onCancel, req, t }: Clarify
   )
 }
 
+export function ConfirmPrompt({ onCancel, onConfirm, req, t }: ConfirmPromptProps) {
+  const [sel, setSel] = useState(0)
+
+  useInput((ch, key) => {
+    if (key.escape || (key.ctrl && ch.toLowerCase() === 'c')) {
+      onCancel()
+
+      return
+    }
+
+    const lower = ch.toLowerCase()
+
+    if (lower === 'y') {
+      onConfirm()
+
+      return
+    }
+
+    if (lower === 'n') {
+      onCancel()
+
+      return
+    }
+
+    if (key.upArrow && sel > 0) {
+      setSel(0)
+    }
+
+    if (key.downArrow && sel < 1) {
+      setSel(1)
+    }
+
+    if (key.return) {
+      sel === 0 ? onCancel() : onConfirm()
+    }
+  })
+
+  const accent = req.danger ? t.color.error : t.color.warn
+  const confirmLabel = req.confirmLabel ?? 'Yes'
+  const cancelLabel = req.cancelLabel ?? 'No'
+
+  const rows = [
+    { color: t.color.cornsilk, label: cancelLabel },
+    { color: req.danger ? t.color.error : t.color.cornsilk, label: confirmLabel }
+  ]
+
+  return (
+    <Box borderColor={accent} borderStyle="double" flexDirection="column" paddingX={1}>
+      <Text bold color={accent}>
+        {req.danger ? '⚠' : '?'} {req.title}
+      </Text>
+
+      {req.detail ? (
+        <Box paddingLeft={1}>
+          <Text color={t.color.cornsilk} wrap="truncate-end">
+            {req.detail}
+          </Text>
+        </Box>
+      ) : null}
+
+      <Text />
+
+      {rows.map((row, i) => (
+        <Text key={row.label}>
+          <Text color={sel === i ? accent : t.color.dim}>{sel === i ? '▸ ' : '  '}</Text>
+          <Text color={sel === i ? row.color : t.color.dim}>{row.label}</Text>
+        </Text>
+      ))}
+
+      <Text color={t.color.dim}>↑/↓ select · Enter confirm · Y/N quick · Esc cancel</Text>
+    </Box>
+  )
+}
+
 interface ApprovalPromptProps {
   onChoice: (s: string) => void
   req: ApprovalReq
@@ -164,3 +238,10 @@ interface ClarifyPromptProps {
   req: ClarifyReq
   t: Theme
 }
+
+interface ConfirmPromptProps {
+  onCancel: () => void
+  onConfirm: () => void
+  req: ConfirmReq
+  t: Theme
+}